The present invention has as its object a process and a device for executing the screwing of threaded joints for steel tubes, equipped with a stop which can be used, in particular, in the petroleum industry.
It is known that threaded joints for tubes which connect, in an impervious and detachable fashion, sections of tubes which are placed end to end to make columns are currently used in the petroleum industry.
Such joints have male and female threads which are most generally tapered (but may occasionally be cylindrical), as well as impervious surfaces which come into contact during screwing down of the joint, and in most cases, screwing limit stops, the purpose of which is to suddenly increase the screwing torque so as to immobilize the two elements of the joint in a predetermined position.
Acccording to the state of the art, the screwing of joints in the workplace is carried out by connecting one of the elements of the joints with the other by screwing torque which is located within a domain predetermined by the joint manufacturer.
Thus, this operating method does not provide total satisfaction because, for a given screwing torque the conditions of tightening may vary to a large extent from one joint to another. In fact, due to manufacturing tolerances, resulting especially from differences in diameter of the male and female threads, as well as shifts in position of the screwing limit stops relative to the threads, the torque which is required to insure, for example, the fitting of tapered threads until the surfaces of the screwing limit stops come into contact, may vary in significant proportions, and the torque subsequently applied for tightening the screwing limit stops varies in the same fashion, but in the opposite direction. In addition, the greases used for the mounting of joints do not always have the same characteristics, which also results in a variation in the torque absorbed by the fitting in the threading.
Under these conditions, it is understood that joints reputed to be identical and screwed with the same tightening torque do not present the same conditions of operational reliability, in which a more or less large total screwing torque is absorbed by the fitting of the threads and/or by the tightening of the screwing limit stops.